ECHO Build Log/Building up an old PC (Need help and opinions on things along the way!)

QuadRings

Reputable
Jan 14, 2015
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Alright then. So recently, I finally got an old PC from some relatives to build in. It is my first desktop. As such, I need help along the way building this thing up, and other things. Ill post pictures of it in my next post, but here are the specs:
eMachines T5224
Pentium D 820 2.8 GHz
Stock cooler with aftermarket fan (Max clearance: 130mm)
Intel GMA950 Graphics
1GB RAM DDR2
200GB SATA 2 HDD
Windows Vista
Gateway Coryville 945G motherboard
DVD Burner (LG)
BesTec 350W
eMachines E19T5W 900P LCD monitor

The following parts have been installed:
200GB SATA 2 HDD (Seperate disk with a different OS to be installed)

I have the following to install:
Windows 7 Home Premium (Taken off an old computer. Im going to install it on the eMachines, and if I cannot activate it, Ill contact Microsoft and claim Im "repairing" the original PC)

I have the following on order:
4GB Crucial DDR2 RAM
AULA Keyboard (Stock one shorted yesterday in transit :()
Arctic Silver 5 Thermal Paste

It is insanely dirty and must be clean, but Ill get to it before anything else. I also have an eMachines EL1331G-01W to steal parts (and the W7) off of.

So what I need is h3lp and/or advice on the way to making this a truly powerful PC, and I hope you guys can help with Parts, mods and such. Thank You!

First question: best way to clean it? Vacuum or Canned air?